NPE when NetconfDeviceSalProvider.close

NPE observed during bgpcep-csit-3node-periodic-bgpclustering-only-carbon test

org.opendaylight.netconf.sal.connect.netconf.sal.NetconfDeviceSalProvider@366a9057
java.lang.NullPointerException
at org.opendaylight.netconf.sal.connect.netconf.sal.NetconfDeviceSalProvider.close(NetconfDeviceSalProvider.java:115)[343:org.opendaylight.netconf.sal-netconf-connector:1.5.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.MasterSalFacade.closeGracefully(MasterSalFacade.java:170)[346:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.MasterSalFacade.close(MasterSalFacade.java:122)[346:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.utils.NetconfConnectorDTO.close(NetconfConnectorDTO.java:45)[346:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.RemoteDeviceConnectorImpl.stopRemoteDeviceConnection(RemoteDeviceConnectorImpl.java:154)[346:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.NetconfTopologyContext.closeServiceInstance(NetconfTopologyContext.java:98)[346:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.mdsal.singleton.dom.impl.ClusterSingletonServiceRegistrationDelegator.closeServiceInstance(ClusterSingletonServiceRegistrationDelegator.java:52)[182:org.opendaylight.mdsal.singleton-dom-impl:2.2.0.SNAPSHOT]
at org.opendaylight.mdsal.singleton.dom.impl.ClusterSingletonServiceGroupImpl.lostOwnership(ClusterSingletonServiceGroupImpl.java:338)[182:org.opendaylight.mdsal.singleton-dom-impl:2.2.0.SNAPSHOT]
at org.opendaylight.mdsal.singleton.dom.impl.ClusterSingletonServiceGroupImpl.ownershipChanged(ClusterSingletonServiceGroupImpl.java:238)[182:org.opendaylight.mdsal.singleton-dom-impl:2.2.0.SNAPSHOT]
at org.opendaylight.mdsal.singleton.dom.impl.AbstractClusterSingletonServiceProviderImpl.ownershipChanged(AbstractClusterSingletonServiceProviderImpl.java:146)[182:org.opendaylight.mdsal.singleton-dom-impl:2.2.0.SNAPSHOT]
at org.opendaylight.mdsal.singleton.dom.impl.DOMClusterSingletonServiceProviderImpl.ownershipChanged(DOMClusterSingletonServiceProviderImpl.java:23)[182:org.opendaylight.mdsal.singleton-dom-impl:2.2.0.SNAPSHOT]
at org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnershipListenerActor.onEntityOwnershipChanged(EntityOwnershipListenerActor.java:44)[234:org.opendaylight.controller.sal-distributed-datastore:1.5.0.SNAPSHOT]
at org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnershipListenerActor.handleReceive(EntityOwnershipListenerActor.java:33)[234:org.opendaylight.controller.sal-distributed-datastore:1.5.0.SNAPSHOT]
at org.opendaylight.controller.cluster.common.actor.AbstractUntypedActor.onReceive(AbstractUntypedActor.java:28)[227:org.opendaylight.controller.sal-clustering-commons:1.5.0.SNAPSHOT]
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:165)[200:com.typesafe.akka.actor:2.4.16]
at akka.actor.Actor$class.aroundReceive(Actor.scala:496)[200:com.typesafe.akka.actor:2.4.16]
at akka.actor.UntypedActor.aroundReceive(UntypedActor.scala:95)[200:com.typesafe.akka.actor:2.4.16]
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)[200:com.typesafe.akka.actor:2.4.16]
at akka.actor.ActorCell.invoke(ActorCell.scala:495)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.Mailbox.run(Mailbox.scala:224)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.Mailbox.exec(Mailbox.scala:234)[200:com.typesafe.akka.actor:2.4.16]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]